Electromigration effect on pancake type void propagation near the interface of bulk solder and intermetallic compound

Due to the reduction in the size of electronic devices and solder interconnects, their current densities are rapidly increasing and the effect of electromigration becomes more critical to interconnect failure. Traditional methods are not sufficient to determine the failure mechanisms of solder interconnects under such high current densities. An approach to predict the electromigration effect upon interconnect failure including void propagation is timely and useful to the electronics industry. The stress gradient in a 95.5Sn-4Ag-0.5Cu eutectic solder with a void defect is analyzed numerically to determine the electromigration and stress migration forces. A kinetic mass diffusion model is developed to predict void width and propagation speed near the interface between the intermetallic compound and bulk solder caused by electromigration. A three-dimensional finite element analysis has been performed to analyze the current crowding effect in the interconnect. The proposed kinetic model gives a reasonable prediction for the void width and propagation velocity as compared with experimental results.